Not OP, but I doubt their board's build quality is indicative, really. The C and non-pro K series are wholly like different boards, at a different price point. All plastic, and while they're sturdy enough, it's nothing special.
Source: I have a K2. Compared to my wife's Epomaker TH80, I prefer the Epomaker in terms of build. But it's not like the K2 is bad, or anything. I'd expect the C series to be mostly comparable.